Iron and tin phosphide as polymer electrolyte membrane fuel cell cathode catalysts

A new set of catalysts based on metal-phosphorus/nitrogen-carbon, for the electroreduction of molecular oxygen at the polymer electrolyte membrane fuel cell cathode are reported. These catalysts were simply made from folic acid, phosphoric acid, iron or tin oxides. In particular, the tin oxide-based catalyst exhibited superior electrocatalytic activity against state-of-the-art non-platinum-based catalysts with a mass activity of 6 mA mg−1. Successful application of these catalysts at the cathode of a self-breathing fuel cell is also demonstrated, and this validated the suitability of the catalyst to operate under fuel cell conditions. A power density of 12.6 mW cm−2 at ambient condition (25 °C, 20% relative humidity and dry hydrogen) was achieved. This work provides foundation for the emergence of phosphorous based non-platinum catalysts for fuel cell cathodes.